Three Parrots

A man is selling three parrots.

Another man who wants to buy a parrot approaches him and asks, "How much are your parrots?"

The salesman answers, "The first one is $1,000."

"What does he know?"

"He knows 10,000 words and 500 sentences and is able to solve mathematical expressions."

"How about the second one?"

"The second parrot costs $5,000."

"What does he know?"

"He knows 100,000 words and 10,000 sentences, is able to solve mathematical expressions, and create computer programs."

"Then what is the price for the third one?, the buyer is wondering."

"This one costs $20,000."

"Really?!, wonders the exciting buyer. What does he know?"

"This one knows absolutely nothing, but the two others always call him 'THEIR BOSS.'"